For many of us, a little time with our smartphones or iPads before sleep is the highlight of the night. But would you still think it is relaxing if you knew that it damages or destroys your sleep? Scientists say that's exactly what it does.
In ancient times, when there were no lamps, telephones or smartphones, the sun was the main source of light. When the sun went down, our brains took that as a signal to start producing melatonin(褪黑素), a chemical that helps us sleep.
However, a healthy amount of melatonin can only be produced in complete darkness.Any light in your bedroom—even the one on the alarm clock or the charging indicator on your cellphone—could disturb the process, not to mention something as bright as smartphone and iPad screens. We tend to hold these much closer than a television or laptop, which allows them to shoot far more light straight into our eyes.
“This is particularly worrisome in populations such as young adults and adolescents, who already tend to be night_owls，” said researcher Brittany Wood at Rensselaer Polytechnic Institute.“Lack of sleep among teens is leading to depression, selfharm, low concentration and poor performance at school，” she added.
While all lights are the enemy of sleep, not all colors of light have the same effect. Our eyes are particularly sensitive to blue light, which is common during the day. Most of the light coming from electronic screens is blue light and it fools our brain into thinking it's still daytime. By contrast, orange or red light has less influence on melatonin production, because our brains recognize it as a signal that the day is ending, according to The Telegraph.
Asking yourself to keep your hands off your smartphone before bedtime might seem unreasonable, but you should at least remember to dim the screen or hold it farther away from your eyes. You could also wear a pair of orange sunglasses that take away the harmful blue light.
According to the passage, we can know ________.

A．it's a good habit to play with smartphones or iPads late into night

B．scientists suggest we should avoid using smartphones or iPads

C．darkness makes a great impact on the amount of melatonin

D．the sun was the only source of light in ancient times

Which of the following is TRUE according to the passage?

A．The darker it is, the more melatonin will be produced.

B．The lighter it is, the more melatonin will be produced.

C．The more melatonin you have, the worse you'll sleep.

D．The more electrical equipment you have, the more melatonin will be produced.

The underlined part in Paragraph 4 refers to those ________.

A．who are young adults or adolescents

B．who don't perform well in school

C．who are addicted to a television or laptop

D．who are short of sleep at night and perform poorly in daily life

In the writer's opinion, which is a correct suggestion?

A．You should go to bed when the sun goes down.

B．You should use an orange or red light electronic screen.

C．You should wear a pair of blue sunglasses when sleeping.

D．You should avoid blue light as possible as you can before bedtime.